Brigham Young University BYU ScholarsArchive Theses and Dissertations 1975-07-11 Two new species of the genus cycadeoidea from the lower cretaceous of Utah H. Blaine Furniss Brigham Young University - Provo Follow this and additional works at: https://scholarsarchive.byu.edu/etd BYU ScholarsArchive Citation Furniss, H. Blaine, "Two new species of the genus cycadeoidea from the lower cretaceous of Utah" (1975). Theses and Dissertations. 8056. https://scholarsarchive.byu.edu/etd/8056 This Thesis is brought to you for free and open access by BYU ScholarsArchive. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. !;!d,- L TWONEW SPECIES OF THE GENUSCYCADEOIDEA f _,I FROMTHE LOWERCRETACEOUS q,,) OF UTAH A thesis Presented to the Department of Botany and Range Science Brigham Young University In Partial Fulfillment of the Requirements for the Degree Master of Science by H. Blaine Furniss August, 1975 This thesis, byH. Blaine Furniss, is accepted in its present .. form by the Department of Botany and Range Science of Brigham Young University as satisfying the thesis requirement for, the degree of Master of Science. ii TABLEOF CONTENTS LIST OF ILLUSTRATIONS . V ACKNOWLEDGEMENTS. vi INTRODUCTION. 1 Location and Collection Site. 1 Preservation. 3 Stratigraphy of the Cedar Mountain Formation. 4 Age of the Cedar Mountain Formation . 5 Paleoecology. 5 Cycadeoid Origin. 7 Comparison of Cycads and Cycadeoids 8 Distribution. 9 Derivation of the Generic Name • . 10 MATERIALSAND METHODS .. .. 12 SYSTEMATICPALEOBOTANY. 14 Cycadeoidea medullara •· . 14 Description . 14 General features . 14 Stele . 14 Cortex. 16 Leaf bases . 16 Cones • . 18 Discussion . 24 Comparison with Similar Species . 30 iii Cycadeoidea cleavelandii . • . 33 Description . • . • . • . • . 33 General features . • . • . 33 Stele . 33 Cortex . • . • . 34 Leaf bases . • . • . • . 35 Cone . 36 Discussion . • . • . • • . • 36 Comparison with Similar Species 38 LITERATURECITED . 40 PLATES. • . 44 iv LIST OF ILLUSTRATIONS Figure Page 1. Index Map of Collection Site . • •.••• 2 2. Cycadeoidea medullara. L~af Base Vascular Pattern. 17 3. Cycadeoidea cleavelandii. Leaf base Vascular Pattern 17 4. Cycadeoidea medullara. Young Ovulate Cone. • • • . • 20 5. Cycadeoidea medullara. Reconstruction of Bisporangiate Cone • • • . • • • • 21 6. Cycadeoidea medullara. Reconstruction of Cut Away Side and End View of Chambered Synangium • • • • • • • . 23 7. Cycadeoidea medullara. Reconstruction of Longitudinal View of Seed Stalk and Ovuliferous Scale . • • • • • 23 Plate I. Explanation of Plate I . 45 II. Explanation of Plate II 47 III. Explanation of Plate III 49 IV. Explanation of Plate IV . 51 V. Explanation of Plate V 53 VI. Explanation of Plate VI . 55 VII. Explanation of Plate VII . 57 VIII. Explanation of Plate VIII • 59 IX. Explanation of Plate IX. 61 X. Explanation of Plate X 63 V ACKNOWLEDGMENTS I am indebted to Harry and June Cleaveland of Moab, Utah, who were kind enough to donate several specimens from their collection to the Brigham Young University. They also assisted in the discovery and collection of additional material at the collection site. I also thank Dr. W. D. Tidwell of the Department of Botany and Range Science of Brigham Young University and members of the conunittee who critically reviewed the manuscript and assisted in the completion of this study. James V. Allen of the College of Biological and Agri- cultural Science was very helpful in the production of plates. vi INTRODUCTION The fossil bearing Lower Cretaceous Cedar Mountain Formation near Moab, Utah, U.S.A., has yielded a variety of petrified cycadeoid stems (text fig. 1). This thesis is a report on two species of Cycad- eoidea that were selected for study from among the several stems col- lected. Fragments of cycadeoid stems have been found from other local- ities in the state, but this,area has yielded the greatest concentra- tion of cycadeoid stems to date. Harry and June Cleaveland of Moab discovered the collecting site. They donated several trunks to the Brigham Young University and aided the University in the discovery and collection of six additional trunks from the same area. Most of the specimens were found completely eroded from the sandstone. Other trunks, only partially exposed, were recovered by excavation. Further study of the specimens was conducted in the laboratory. Anatomical investigation was undertaken to determine affinities with previously described genera. Data obtained may reveal specific and phylogenetic relationships among Early Cretaceous cycadeoids. This study represents the first description of cycadeoid stems from Utah and provides additional information on the diverse floral composition of the Cedar Mountain Formation. Location and Collecting Site Specimens were collected from a bluff three miles east of the 1 • 2 CRESCENT JUNCTION 50 6 Highway 160 1 3 miles N Canyon lands • SITE Airfield UTAH Grand County enlarged area 1 100 miles Fig. 1. Index map of collection site. 3 Canyonlands Airfield, NWNEsection 22, T24S, R20E, in Grand.County, Utah (fig. 8). Upper Jurassic Morrison shales form the sloping sides of the bluff and underlie the more resistant Cedar Mountain sandstone cap (fig. 9)_. Most of the cycadeoid trunks were weathered from the sandstone and were partially or fully exposed on the north and west facing shale slopes amidst talus from the sandstone rim. Three trunks were found still embedded in the sandstone (fig. 10). Several large logs of conifer wood were found associated with the cycadeoids. Where trunks and wood fragments were abundant, the sediments tended to be pebbly conglomerates rather than sandstone. Since all fossil material had been transported, this indicated the higher energy turbulence present at the time of deposition. The buff colored Cedar Mountain Formation is a fluvial sand- stone. In the general area of the collecting site the texture varies from coarse sandstone with limestone and clay lenses to a pebbly con- glomerate. Fresh exposures are light brown to light green. Bedding is irregular. Cementation is weak, but Cedar Mountain strata does not weather as readily as the overlying Cretaceous Mancos Shale or the underlying Jurassic Morrison Formation. Where exposed, Cedar Moun- tain strata forms ridges and ledges on the Morrison. Preservation Specimens represented in the collection are silicified petri- factions of monoaxial trunks with attached leaf bases and cones. The exterior of some trunks is often obscured by both sandstone and CaC03 deposits. Weather cracks are severe in some parts of the specimens. Parts of the cortex and leaf bases have been secondarily replaced 4 with clear quartz. Macroscopically, there is little distortion from the original shape. Cellular detail is occasionally obliterated and much of the apparent detail fades with magnification. Stratigraphy of the Cedar Mountain Formation Originally, the Cedar Mountain Formation was defined as part of the Jurassic Morrison Formation (Eldridge 1896). When Knowlton (1920) described Cretaceous age plant remains in the upper portion of the type section, W. T. Lee who had discovered the plant remains, re- moved the upper shale and conglomerate units and placed them in the Dakota Group (Lee 1920). The Morrison Formation was defined as those continental sediments of Jurassic age only (Baker, Dane, and Reeside 1936). Stokes (1944) introduced the formation names Buckhorn Conglom- erate and Cedar Mountain Shale and described these units as lying between Morrison and Dakota sediments. He later defined the upper Cedar Mountain Shale and basal Buckhorn Conglomerate as being members of the Cedar Mountain Formation (Stokes 1952). Similar deposits, stratigraphically equivalent to the Cedar Mountain Formation in south- western Colorado, were originally referred to as the Post-McElmo beds (Coffin 1921). Renamed the Burro Canyon Formation (Stokes and Phoenix 1948), these beds were found by Young (1960) to be physically contin- uous with Cedar Mountain strata west of the Colorado River and he sug- gested that since Cedar Mountain was the prior name, these sediments also be referred to as Cedar Mountain. Cedar Mountain strata are exposed throughout much of eastern Utah, western Colorado and north- central New Mexico. 5 Young (1960) divided the Cedar Mountain Formation into upper, middle and lower units. Because of erosion he was unable to directly trace the Buckhorn from the type area southeast from the San Rafael Swell, but suggested that a probable correlative of conglomeritic sandstone existed in the Moab area. He referred to it as the lower Cedar Mountain-Buckhorn Sandstone, and noted that it becomes more con- glomeritic towards the San Rafael Swell. The middle Cedar Mountain Sandstone also becomes more conglomeritic as it approaches the San Rafael area (Young 1960). The collecting site is at the northern limit of the lower unit in central Grand County, Utah. Since the middle Cedar Mountain Sand- stone is widespread in this area, the plants represented in this study are probably from the middle Cedar Mountain Sandstone. Neither the upper member of the Cedar Mountain nor the Dakota is present at the collecting site. Age of the Cedar Mountain Formation Collections of non-marine microfossils, plants, and molluscs by Stokes (1952) indicated that the Cedar Mountain Formation is Early Cretaceous in age.· Collections by Young(l960) support this conclusion